Laminated sheets (otherwise referred to as “laminate substrates”) are generally used for decorative purposes in many areas of daily life. They are used, for example, in interior construction for the covering or lining of windows, stairs, and floors, and in the coating of furniture, both in the private as well as in the commercial sectors.
Laminated sheets often are made of cellulose sheets impregnated with curable synthetic resins and pressed with heat under high pressure. One or more sheets on one or two sheet sides exhibit decorative colors or decorations. Such laminated sheets (known as high pressure laminates or HPL) are sold, for example, by Resopal GmbH (a Wilsonart International company), under the tradename RESOPAL®.
The application of the laminated sheets on a carrier substrate such as chipboard, fireboard, or plywood used for wall, floor or ceiling finishes or other objects, can be done with an aqueous adhesive. Depending on the type of the adhesive, various conditions must be precisely maintained, so as to obtain a coating of good quality and stability. According to known application methods, the laminated sheets and the carrier are typically joined together after the application of the adhesive, immediately or after a short waiting time. The joining together is done according to the previous methods under a pressing pressure of 2 to 5 bar and at a temperature of up to 120° C.
Furthermore, the adhesive application is typically uniformly distributed over the laminated sheet and/or carrier surface, so as to avoid warp phenomena. This is particularly true for water-containing adhesive systems, in which the application quantity is to be kept as low as possible.
With a nonuniform adhesive application and an inexact maintenance of the pressing pressure, pressing temperature, and/or pressing time, unsatisfactory results can be obtained during the cementing. Thus, for example, excessively high temperatures can lead to warping and material damage. Low temperatures or pressures often result, on the other hand, in an insufficient adhesion. Depending on the adhesive system, the pressing pressure and the pressing temperature typically must be maintained between a few minutes and up to several hours. If necessary, one must wait overnight to obtain a final curing.
Working with solvent-containing contact adhesives generally requires adherence to work protection and accident prevention regulations. Furthermore, the use of solvent-containing adhesives is generally classified as problematic from a health and environmental policy viewpoint. The use of dispersion adhesives on a water basis, such as casein glue, frequently leads to the partial swelling of the carrier surface, which is frequently the case, for example, when using particleboard as the carrier material. As a result, a slightly corrugated or nonuniformly plane surface is obtained. Furthermore, the drying of water- or solvent-containing adhesives may require several hours.
Reaction adhesive, such as epoxide, polyesters, or polyurethane adhesives, are also of concern with respect to health and require a precise knowledge and maintenance of the processing conditions.
The previous adhesives and adhesive methods typically require a high equipment outlay, such as, for example, for the use of uniform and high pressing pressures and for the maintenance of the temperature. Depending on the adhesive, the curing, e.g., until a sufficient adhesive is attained, can require several hours.
The circumstances mentioned above often make the use and the successful processing of laminated sheets relatively difficult, particularly for the private sector or in the craftsman's sector. There is a need for an improved, efficient, safe, and less expensive decorative laminate panel.